Meira Chand has for 30 years turned an outsider's acute eye on the societies in which she has lived in Asia, mainly Japan and India. Her eighth novel is a panoramic page-turner set in colonial Singapore. Like JG Farrell's The Singapore Grip, A Different Sky leads up to the Japanese invasion described by Churchill as the "largest capitulation in British history". Yet the focus is less on the delusions of a faltering empire than on the turmoil of the brashly emergent city-state.

Stretching from Chinatown riots in 1927 to pro-independence rallies during the Malayan emergency in the mid-1950s, the main thread is a tenacious, forbidden passion between a Eurasian boy and a Chinese girl. Howard Burns and Mei Lan cross paths as children when their bus is caught up in the first rioting sparked by Chinese communists. Howard's widowed mother Rose – born in Malacca of a "confusing line of swarthy intermarriage" stemming from Portuguese, Dutch, British and Irish men and Malay, Indian, Chinese and Ceylonese women – runs a boarding house for Englishmen on tours of duty, and combines Anglophilia with a love of local saltfish pickle. Across the storm canal is the villa of Mei Lan's tycoon grandfather, once a tin mine coolie, and his various wives. Though the tycoon's generation looks back to China, Mei Lan's mother is English-educated Straits Chinese, and the often thwarted lovers gradually affirm roots in Singapore.

According to one lodger, the Eurasians, English-speaking Christians, "push our pens for us". As Howard sees it, the men who followed Stamford Raffles had bred a hybrid "race of mimic men trained to serve the new colony". Smiling at a blonde woman, Rose "in reply received a cool stare of query". Howard chafes at such condescension towards "locals", and neither he nor his sister Cynthia heed their mother's advice to "keep to their own". When Cynthia's hazel eyes catch those of Wilfred Patterson, a newly arrived reporter on the Straits Times, an old hand warns him: "A man's career is finished if he takes a dusky-skinned wife . . . you'll be cut dead by everyone who matters."

As this stratified society faces wartime upheaval, intersecting characters signal shifting political affiliations. The upwardly mobile Raj Sherma, a recent arrival from India, ignores the boycott of Japanese goods following the invasion of Manchuria, and profits from the war. His friend Krishna openly backs the Japanese-allied Indian independence fighter Subhas Chandra Bose. But Howard signs up to fight the Japanese in the mangrove swamps before the ignominious surrender. When his mother's boarding house is requisitioned, he takes refuge with the communist guerrillas in the jungle, while Mei Lan, now a nurse, is brutally interrogated amid the atrocities of occupation.

The novel traces the impact of the war on a region-wide ferment for freedom – including women's. As one of Howard's colleagues says: "The British think they're returning to the old order of things. [But] if the Japanese could get the British out, then so can we." When Wilfred returns as a PoW from building the Thai-Burma railway, he is set upon by Malay nationalists. Meanwhile, in the rising lawyer Lee Kuan Yew, Howard discerns an "impatience and intolerance in the shrewd chiselled face".

There are subtle echoes between the characters' need to forget in order to heal, and that of a nation built largely of diasporic peoples. For Krishna, Singapore is a "transient place; it has no ancient culture; it is nobody's homeland. People come to make money, and then return home." Yet the opportunistic Raj comes to realise the limitations of an overriding "determination to prosper" .

The epic sweep can be vertiginous – Mei Lan moves from tycoon's daughter and torture victim to Oxford-trained lawyer championing women's rights – with some overly neat plot devices. Yet this meticulously researched book is alive with engrossing detail, whether on the odour of Chinatown, the privations of a guerrilla camp or the appalling rituals of foot binding. Enriched by oral histories, itstays true to the perspective of its prologue, which evokes those who voyaged over the China sea and the Indian ocean to make the "pinprick" of Singapore island their home.